A heterologous booster vaccination strategy against Covid-19 can be considered - for logistical reasons and in some cases for more effective protection - according to the European Medicines Agency (EMA) and the European Centre for Disease Prevention and Control (ECDC).
In a report published on Tuesday 7 December, the two institutions state that the data available to date has allowed them to conclude that a booster given with a different vaccine from the one used in the primary vaccination “appears to be as good or better in terms of immune responses than a homologous booster”.
They ensure that combinations of heterologous and homologous boosters remain otherwise comparable in terms of safety.
Regarding the combinations that have shown increased protection, the EMA and ECDC state that it is the combination of viral vector and mRNA vaccines that produces good levels of antibody to the virus that underlies Covid-19 (SARS-CoV-2) and a higher T-cell response than when the same vaccine is used. This applies to both primary and booster vaccinations.
However, both institutions report that the use of a viral vector vaccine as a second dose in the primary vaccination and the use of two different mRNA vaccines are less well studied.
In addition, there is no data on immunocompromised individuals to recommend heterologous vaccination for them.
The EU is currently experiencing an increasing number of infections, as well as rising hospitalisation rates, and figures show that hospitalisations and deaths remain lowest in states with the highest vaccination rates (see EUROPE 12839/9), the EMA and ECDC point out. (Original version in French by Agathe Cherki)